Here's a question for those who know a lot about fitting a pack.

I'm wanting to buy a pack for my daughter and I found one on eBay that I was interested in but the seller didn't list the size. I asked the seller and he said he didn't have the tags and didn't know how to tell the size. He asked if I knew. It had never occurred to me but I realized I would not be able to tell the size of a pack unless I could try it on.

When I have bought packs I have measured my torso (hip to neck like you are supposed to) and then bought the pack that is designed for that length. But what is the measurement you would do on a pack to determine what torso length it is designed for?

It seems like the right thing is to measure from where the shoulder strap is attached to the pack to where the hip belt is attached or something like that. But that's just a guess on my part.